

db.stu.insert([{
    username:"张六",
    password:123456,
    age:28,
    city:"上海"
},{
    username:"张七",
    password:456789,
    age:13,
    city:"杭州"
}])

db.stu.insertOne({
    username:"王二张",
    password:98765,
    age:22,
    city:"上海"
})

db.stu.insertMany([{
    username:"赵五",
    password:123123,
    age:22,
    city:"上海"
}])


db.stu.updateOne({username:"张三"},{$set:{password:"admin"}})

db.stu.updateOne({city:"北京"},{$set:{password:"abcdef"}})

db.stu.updateMany({city:"上海"},{$set:{password:"qwerty"}})

db.stu.updateMany({city:"上海"},{$inc:{age:2}})


// 一页显示num条数据
// 第0页：从0*num开始，查num个
// 第1页：从1*num开始，查num个
// 第2页：从2*num开始，查num个

// 第n页：从n*num开始，查num个

// db.stu.find({},{_id:0,username:1,password:1}).limit(n*num).skip(num);

